1. Field of the Invention
The present invention relates to a projection display apparatus including an imager that modulates light emitted from a light source and a projection unit that projects light emitted from the imager on a projection surface.
2. Description of the Related Art
Conventionally, a projection display apparatus has been known which includes an imager modulating light emitted from a light source and a projection unit projecting light emitted from the imager on a projection surface.
Here, depending on a positional relationship between the projection display apparatus and the projection surface, the shape of the image projected on the projection surface is distorted.
To counter this, a proposal has been made of a method in which a test pattern image projected on a projection surface is captured by a imaging device such as a camera, a positional relationship between a projection display apparatus and the projection surface is determined by detecting characteristic points included in the test pattern image, and the shape of an image is adjusted based on the identified positional relationship (for example, Japanese Patent Application Publication No. 2001-83949).
For example, the following methods are proposed as methods of detecting the characteristic points. Specifically, they are (1) a method of detecting a relative positional relationship among multiple characteristic points (first method), (2) a method of detecting multiple characteristic points by lighting up the characteristic points one by one (second method), (3) a method of detecting multiple characteristic points by lighting up characteristic points at different frequencies (third method), and (4) a method of detecting multiple characteristic points by lighting the characteristic points different in hue (fourth method).
However, there are following problems in the methods described above. Specifically, in the first method, the relative positional relationship among the multiple characteristic points cannot be accurately detected when the entire test pattern image cannot be captured by the imaging device. In the second method, the number of test pattern images in each of which one characteristic point is lighted is large when the number of characteristic points is large, and thus a large memory capacity is required to store the test pattern images. In the third method, differences between the frames have to be detected to detect the characteristic points, and a circuit required for detection of the character points is complicated. In the fourth method, differences (color differences) among the hues of the characteristic points are small when the number of characteristic points is large, and false detection of the characteristic points is likely to occur.